Various methods have been used to mask or "freshen" the air in an enclosed environment (e.g. a room or automobile). For freshening the air in a room, methods used have included burning scented candles or incense or using electrical devices such as that disclosed in U.S. Pat. No. 4,849,606 to Martens et al. (Jul. 18, 1989). Martens et al. discloses a tamper resistant container used to hold a volatile material for slow diffusion. U.S. Pat. No. 5,373,581 to Smith et al. (Dec. 13, 1994) discloses a device somewhat similar to that of Marens et al. for use in an automobile.
Another fragrance emitting system for use in automobiles is disclosed in U.S. Pat. No. 5,171,485 to Ryan (Dec. 15, 1992). The Ryan device consists of a plastic reservoir which houses liquid fragrance, and a pump that extracts the fragrance from the reservoir and transports it to a holder mounted in an air vent. While fine for certain applications, the device is not integrated into a single unit, and evidently relies on an external power source to power the pump.